Hungarian news sites are reporting that director Ridley Scott has explained the connection between the Alien movies and the prequel film Prometheus. There isn't confirmation yet, but if the sites are to be believed, Guy Pearce is the key linking the films. Possible spoilers. Maybe.

This still falls under the category of rumor at this point, but some Hungarian sites say that Scott had an interview with the outlet IC Press, in which he explained Pearce's role in the film (which Pearce has said is about a minute long) and how it connects to Alien:

When the first ‘Alien' movie and ‘Blade Runner' were made, I thought that in the near future the world will be owned by large companies. This is why we have the Tyrell Corporation in ‘Blade Runner', and Weyland-Yutani in ‘Alien'. They sent the Nostromo spaceship.

The Prometheus is owned by an entrepreneur called Peter Weyland, and is played by Guy Pearce. That's the connection between the two films, and nothing more. Prometheus is a new film, a new world, and is full of new ideas. And of course new monsters as well.

New, of course, except for that fact that everything in space wants to kill you.